全文获取类型
收费全文 | 3850篇 |
免费 | 2篇 |
专业分类
化学工业 | 11篇 |
机械仪表 | 1篇 |
轻工业 | 25篇 |
水利工程 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 2篇 |
冶金工业 | 3800篇 |
自动化技术 | 10篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 5篇 |
2003年 | 13篇 |
2000年 | 2篇 |
1999年 | 137篇 |
1998年 | 1252篇 |
1997年 | 779篇 |
1996年 | 475篇 |
1995年 | 232篇 |
1994年 | 215篇 |
1993年 | 219篇 |
1992年 | 19篇 |
1991年 | 31篇 |
1990年 | 35篇 |
1989年 | 46篇 |
1988年 | 31篇 |
1987年 | 26篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 57篇 |
1976年 | 133篇 |
1975年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有3852条查询结果,搜索用时 15 毫秒
81.
A Konijnenberg EW Stokkers JA van der Post MC Schaap K Boer OP Bleker A Sturk 《Canadian Metallurgical Quarterly》1997,176(2):461-469
OBJECTIVES: Platelets play an important role in the pathophysiologic mechanisms of preeclampsia. Our purpose was to investigate by means of flow cytometry to what extent platelets circulate in an activated state during normal pregnancy and whether this activation is more extensive in preeclampsia. STUDY DESIGN: Platelets in whole blood from 10 preeclamptic third-trimester pregnant women (highest diastolic blood pressure range 100 to 130 mm Hg, proteinuria range 0.59 to 11.5 gm/24 hr) and from 10 normotensive third-trimester pregnant controls were analyzed with the following activation markers: anti-P-selectin (alpha-granule secretion), anti-CD63 (lysosomal secretion), PAC-1 (monoclonal antibody against fibrinogen receptor conformation of the glycoprotein IIb/IIIa complex), anti-platelet endothelial cell adhesion molecule-1, and annexin-V (a placental protein that binds to negatively charged phospholipids, present on the outside of the platelet plasma membrane after activation). The differences in surface antigen exposure between the two groups were determined by double-label flow cytometry. Flow cytometric data were analyzed in two ways: first, the percentages of activated platelets above a certain threshold compared with a nonpregnant control sample were determined, indicative for activation of a subpopulation of cells, and, second, the mean fluorescence intensities were determined, indicative of the mean surface antigen expression of the total platelet population. RESULTS: Analysis of the percentage of activated platelets proved most informative. With this analysis an enhanced platelet activation status was present in 4 of 10 normotensive patients and a more extensive platelet activation status in all 10 preeclamptic patients, as indicated by P-selectin (p = 0.008) and CD63 (p = 0.03) expression. Increased platelet endothelial cell adhesion molecule-1 (p = 0.005) expression was also observed in preeclampsia. CONCLUSIONS: Flow cytometric analysis clearly indicated that platelets circulate in a more extensively activated state during preeclampsia than during normal pregnancy. The increased platelet endothelial cell adhesion molecule-1 expression in preeclamptic patients demonstrates that, besides alpha-granular and lysosomal release, other hitherto unknown mechanisms are involved. Platelet endothelial cell adhesion molecule-1 appears to be the best marker to distinguish preeclamptic patients from normotensive pregnant women. Only a subpopulation of the platelets appears to be activated. 相似文献
82.
Increased levels of plasma cholesteryl ester hydroperoxides in patients with subarachnoid hemorrhage
MC Polidori B Frei G Rordorf CS Ogilvy WJ Koroshetz MF Beal 《Canadian Metallurgical Quarterly》1997,23(5):762-767
The pathophysiology of subarachnoid hemorrhage (SAH) may involve free radical production and lipid peroxidation. We examined plasma levels of cholesteryl ester hydroperoxides (CEOOH) and antioxidants in 25 patients with SAH, and 10 neurologic controls with lacunar stroke. Patients with SAH had significantly increased plasma levels of CEOOH, which peaked on day 5 after the ictus. Concentrations of CEOOH were significantly increased, and ascorbic acid concentrations were significantly decreased in patients who developed vasospasm compared with patients without vasospasm. Increased levels of CEOOH were associated with increased mortality and correlated with clinical outcome scales. These results implicate oxidative stress in the pathogenesis of SAH and suggest that measurements of CEOOH in plasma may be useful both prognostically as well as in monitoring therapeutic interventions. 相似文献
83.
84.
85.
86.
More work is necessary to establish corneal dimensions and retinal structure and neural organisation in the equine eye. This paper reports a case of surgical management of bilateral cataracts in a pony and the results of a survey of refractive error in normal horses. Aspects of accommodation are discussed. It is suggested that a difference in retinal receptor organisation between horse and human eyes could explain the good visual performance of the aphakic pony; and that the degree of blurring of vision in the aphakic situation is less, both in absolute terms and in proportion to presumed normal levels of vision, in the horse than in man. It would not seem necessary to consider intra-ocular implants for horses at this stage. The authors feel it is unwise to extrapolate too freely from human data. More information is needed on the optics and retinal topography of many species, particularly horses and dogs, before routine implant surgery on eyes is undertaken. 相似文献
87.
88.
89.
90.
J Hernández Martínez FJ Ruiz López JJ Martínez Garcerán MC Abellán Martínez P Méndez Martínez F Sánchez Gascón 《Canadian Metallurgical Quarterly》1997,33(1):50-51
Foreign body aspiration requires emergency bronchoscopic examination when the product is chemically active. We describe the case of a female patient who aspirated a ferrous sulfate tablet that, in spite of being extracted immediately, caused lesions that persisted in the bronchial tree for 6 weeks. We then discuss the potential of ferrous sulfate substance to cause damage to the tracheobronchial tree. 相似文献